1. Technical Field of the Invention
This invention relates generally to hybrid vehicles and in particular to systems and methods for regenerative braking in hybrid vehicles.
2. Description of Related Art
This section describes related art, and accordingly, the statements in this section are not admissions of prior art.
Fuel efficiency is a personal, national and global issue. A significant portion of energy consumption is the use of gasoline in cars which has resulted in a movement towards hybrid technologies to improve efficiency.
Certain types of hybrid vehicles use both an electric motor and an internal combustion engine. These types of hybrid vehicles combine the driving range of the internal combustion engine with the fuel efficiency and emissions-free characteristics of the electric motor. The electric motor is powered by a battery system with a limited storage capacity.
For such hybrid electrical vehicles, ifs important that the battery system remain charged as long as possible. When the hybrid vehicle battery loses its charge, the internal combustion engine is entirely responsible for powering the vehicle. At that point, the hybrid vehicle loses the fuel efficiency and emissions-free characteristics of the electric motor.
To extend the charge of its battery, hybrid vehicles may employ regenerative braking systems. In regenerative braking systems, for example, when the brakes are applied, the electric motor reverses direction. The torque created by this reversal counteracts the forward momentum and eventually stops the hybrid vehicle. When the electric motor reverses direction during braking, it also becomes an electric generator. The electricity generated during braking is used to recharge the battery in the battery system powering the electric motor. Regenerative braking is thus able to recoup some of the energy produced during the braking process, and this energy is used to recharge the battery that powers the electric motor.
Overall fuel efficiency of a hybrid vehicle may be increased through improved control of the regenerative breaking system and thus extending the use of the electric motor.